Acoustical "Tee Bar" electrical box hangers have been widely employed, in the construction of ceilings, and particularly suspended or drop ceilings. A widely used example is the CADDY.RTM. 512 or 512A box hanger. CADDY.RTM. is a registered trademark of Erico, Inc. of Solon, Ohio. The hanger comprises two clips riveted to the ends of a spanning bar which snap on the bulb end of the stem of the Tee. The box is held to the spanning bar by a spring finger clip embracing the bar which is secured to the back of the box by a threaded fastener. The spanning bar is rectangular and edgewise to the load, with the spring finger including a bent portion extending over the back edge of the bar and clasping the box to the front or lower edge. The 512A hanger includes slotted intermediate brackets between the ends of the spanning bar and Tee bar clips. The spanning bar is secured to the brackets by threaded clamp fasteners.
Another similar box hanger is the ARC-CO drop ceiling bar which utilizes swivel brackets at each end of the spanning bar which are clamped to the Tee bar with a threaded fastener. The box is held to the bar by what is known as a swivel hickey which again uses a threaded fastener manipulated through a relatively large clamp from inside the box.
Other types of systems are employed but commonly use threaded fasteners such as nuts and bolts, cap screws, or sheet metal screws, to hold the box to the bar. To the installer, screws and other detached pieces of a multipart assembly can become a nightmare. The work is usually done on a ladder or scaffold and lost parts or forgotten special tools can be a real time wasting problem which can induce the installer into jury rigged unsafe shortcuts. Moreover, all buildings vibrate, and suspended wire or chain drop ceilings are susceptible to special harmonics. The vibrations may be imperceptible such as those from fan motors, or be more perceptible such as those caused by wind or earthquakes. Accordingly, any fastening system should not only be easy to install, but should also provide a firm yet somewhat yielding connection, and also not be or able to become loose. It would thus be desirable to achieve such a connection with a spring clip and screwless quick mount strut and clip assembly, having all of the flexibility and advantages of the more complex multipart screw fastener type hangers described above. It would also be desirable if the clip could be preassembled with the strut for shipping purposes, and the clip preassembled with the box for ease of installation, the box then acting as a handle for installation of the clip and box on the strut. In this manner, the clip box and strut should be capable of assembly without any tools, even pliers.